This invention relates to a method of manufacturing a semiconductor device and a unit of manufacturing a semiconductor device, wherein a metallic circuit is formed in a recess portion, which includes: a minute through-hole for connecting circuit layers, a minute contact-hole for connecting a circuit layer and a diffusion layer (doped layer) such as a transistor device, and a narrow groove for forming a metallic wire. In particular, this invention relates to a method of manufacturing a semiconductor device and a manufacturing unit for carrying out a part of the method, wherein a good filling can be achieved by controlling a deposition characteristic of an early stage of a deposition process, in which a metal for a circuit is deposited on a base-metal film, which has been pre-deposited in a recess portion and on a plane in which the recess portion is formed, by using a CVD (Chemical Vapor Deposition) method. The term of base-metal film used in the specification also includes any base-metal compound film.
As a semiconductor device being a semiconductor integrated circuit, for example an IC or an LSI, is made more minute, a contact-hole for connecting an impurity-diffusion layer (doped layer) and a metallic-circuit layer and/or a through-hole for connecting metallic-circuit layers, which holes are formed on a surface of a semiconductor substrate, are also made more minute. That is, an aspect ratio (a ratio of an open width with respect to a depth of the hole) of the contact-hole and/or the through-hole is increased.
A method of depositing a metal for a circuit such as an aluminum alloy by means of a sputtering method is conventionally used as an art of obtaining an electric connection by filling such a hole with a metal for a circuit. However, it is difficult to satisfactorily deposit the metal for a circuit in such a minute hole by means of a sputtering method. Thus, it has been studied to adopt a CVD method that is superior in a deposition characteristic into a minute hole.
The CVD method includes: a selective deposition CVD method (selective), wherein a non-electric-conductive area (for example, a surface of an insulating layer formed on a base-metal circuit) and a electric-conductive area (for example, a surface of a base-metal film exposed at a bottom of a hole formed in the insulating layer) are formed on a surface of a substrate, and then a metal for a circuit is deposited only on the electric-conductive area; and a whole-surface deposition CVD method (blanket), wherein a base-metal film such as a titanium nitride film is formed on the whole surface of the substrate including the inside of the hole and the surface of the insulating layer around the hole, and then a metal for a circuit is deposited on the whole surface.
Among them, the whole-surface deposition CVD method has an advantage that a sensitiveness to a state of the surface of the substrate with respect to the deposition is low, so that the method can be used stably as a mass-production art. In addition, the whole-surface deposition CVD method has an advantage that a metal film for a circuit deposited on the insulating layer outside the hole can be patterned to be used as a or more metallic wires.
Tungsten that can be made from tungsten fluoride (WF6) and aluminum that can be made from any organic aluminum compound are typical as an electric conductive metal that can be deposited by means of the above CVD methods. In particular, aluminum is superior because its electric resistance is one third as much as that of tungsten so that a low-resistance circuit element can be formed. In addition, copper and gold whose electric resistance is further lower than that of aluminum can be deposited by means of the CVD methods.
Following two methods are known as an art to fill a hole with aluminum by means of the whole-surface deposition CVD method.
In a first method, a deposition unit is used wherein a CVD reacting chamber and a sputtering chamber are connected to each other via a transferring chamber that is shut off from the atmosphere. At first, titanium nitride is deposited on the whole surface of a substrate, in which a hole has been formed, in the sputtering chamber. Then, the substrate is transferred into the CVD chamber through the transferring chamber without being exposed to the atmosphere. Next, aluminum is deposited by means of a CVD method using triisobutyl aluminum (for example, see U.S. Pat. No. 5,008,217). However, in practice, the sputtering chamber and the CVD chamber are very different in their using gas and their operating pressure. Thus, it is technically difficult to both form and use the unit in which the sputtering chamber and the CVD chamber are united.
In a second method, titanium nitride is deposited on the whole surface of a substrate, in which a hole has been formed, by means of a sputtering method. The substrate is introduced into a CVD unit. Then, the substrate is allowed to come in contact with the atmosphere. After that, aluminum is deposited by means of a CVD method using dimethyl-aluminum-hydride (for example, see 1993 VLSI Multilevel Interconnection Conference Symposium p.463). In the case, if a substrate temperature at a CVD process is set to a value that can achieve a high deposition rate, aluminum deposited on the insulating layer outside the hole may cover an opening at an upper portion of the hole, before the minute hole is filled up. That is, a hollow void may be formed in the hole, so that a good filling can not be achieved. Thus, in order to achieve a good filling, it is necessary to lower the substrate temperature at the CVD process. However, in that case, the deposition rate is also lowered, so that the efficiency of the mass production is lowered.
On the other hand, the following method is known regarding the case wherein a hole is filled with tungsten by means of the selective deposition CVD method.
In this method, an unit is used wherein a cleaning chamber and a CVD chamber are connected to each other via a transferring chamber that is shut off from the atmosphere. At first, a surface such as a metallic surface exposed at a bottom of the hole is cleaned by plasma including hydrogen and/or halogen gas in the cleaning chamber. The substrate is transferred into the CVD chamber through the transferring chamber without being exposed to the atmosphere. After that, tungsten is deposited selectively only in the hole by means of a CVD method using tungsten fluoride. For example, U.S. Pat. No. 5,043,299 discloses an art to remove contaminants such as water vapor or any oxide attached in the atmosphere, which may obstruct the deposition of tungsten, by using plasma, regarding a surface such as a metallic surface exposed at a bottom of a hole.
In addition, when a metallic circuit is formed, a conventional method has been used wherein: a metal for a circuit such as an aluminum alloy is deposited on the whole upper surface of a base insulating layer by means of a sputtering method, an unnecessary part thereof is removed by means of a photo lithographic art and a dry etching art, and hence a metallic circuit layer including a desired circuit pattern is formed. However, as the metallic circuit becomes so minute that it becomes more difficult to carry out the dry etching process to the circuit layer, another method has been proposed wherein: narrow grooves corresponding to a metallic circuit pattern (grooves for a circuit) are formed in the surface of the insulating layer in advance, and a metal for a circuit is formed in the grooves (for example, see U.S. Pat. No. 4,789,648). In the case too, it is preferable that a metal for a circuit for forming a circuit layer is deposited by means of a CVD method superior in an ability to fill narrow grooves therewith.
In addition, as the JP publication No.6-35657 discloses, there is another method of depositing an aluminum film, wherein a surface activation layer of a hydroxyl group (in which a hydrogen ion in the hydroxyl group is replaced with an organic, inorganic or organic-metallic ligand group or with a metallic ion such as a Cr ion or an Al ion) is formed on a surface of a substrate by treating said surface.
Thus, in order to fill up a narrow hole or a narrow groove for a circuit formed in an insulating layer with a metal for a circuit, it is preferable to use a CVD method superior in step-coverage performance. However, the conventional CVD methods have a large number of steps and/or need complicated steps. That is, a depositing method that achieves sufficient filling performance with simple steps has not been proposed yet.
This invention is intended to solve the above problems.
The object of this invention is to provide a manufacturing method and a manufacturing unit of a semiconductor device, that can satisfactorily fill a minute hole or a minute groove for a circuit with a metal for a circuit and that can form a circuit layer, with a small number of and simple steps.
The inventors conducted various experiments and analysis, about a previous step using an organic solvent having an OH-group and about a CVD step conducted thereafter.
As a result, the inventors have found that the condition of the previous step may have a great effect on the deposition of a metal for a circuit in the CVD step.
The invention is a method of manufacturing a semiconductor device by forming a plurality of films on an insulating layer which has a surface in which a recess portion is partially formed, the method comprising: a base-metal-film forming step of forming a base-metal film including a metal having a high melting point on the surface of the insulating layer including an inside surface of the recess portion; a surface-processing step of processing a surface of the base-metal film by means of an organic solvent having an OH-group; and a metal-for-circuit depositing step of depositing a metal for a circuit on the processed surface of the base-metal film by means of a CVD method in such a manner that at least a part of or the whole of the recess portion is filled up.
According to the above feature, substances stuck on the surface such as contaminants can be effectively removed by conducting the surface-process by means of the organic solvent having an OH-group, before depositing the metal for a circuit by means of the CVD method. Thus, the minute recess portion can be filled up at least satisfactorily. In addition, if the depositing step is continued, it also becomes possible to form a circuit layer (a deposited layer) having a uniform thickness.
In addition, preferably, the method includes: a circuit-layer forming step of forming a circuit layer by depositing a metal for a circuit by means of a sputtering method or a electroplating method, after the metal-for-circuit depositing step.
Preferably, the method of forming the metal for a circuit can be switched from the CVD method to a sputtering method. In the case, the whole depositing time can be shortened to improve the throughput, compared with a case wherein all necessary thickness is deposited by means of the CVD method. In addition, a sputtered film that is more durable to electromigration or the like can be formed as the circuit layer.
Alternatively, after the metal-for-circuit depositing step, a removing step of removing the deposited metal layer while leaving the metal for a circuit filling the recess portion and a new circuit-layer forming step of forming a circuit layer by depositing a metal for a circuit on the whole surface by means of a sputtering method or a electroplating method may be conducted.
In the case, the deposited layer is removed while leaving the metal for a circuit deposited to fill the recess portion by the CVD method, and a new circuit layer may be formed by the sputtering method. That is, the former circuit layer can be replaced with the metal for a circuit that has a better film quality.
In addition, in the surface-processing step, it is preferable that a gaseous organic solvent is adapted to come in contact with the base-metal film. Alternatively, in the surface-processing step, a liquid organic solvent is adapted to come in contact with the base-metal film.
The recess portion may be a contact-hole formed in the insulating layer. Alternatively, the recess portion may be a through-hole formed in the insulating layer. Alternatively, the recess portion may be a groove for a circuit formed in the insulating layer.
For example, the metal for a circuit is Al or Cu.
In addition, the invention is a manufacturing unit of a semiconductor device comprising: a surface-processing unit that causes a surface of a semiconductor device material to come in contact with an organic solvent having an OH-group to conduct a surface-process; a CVD unit that deposits a metal for a circuit on the surface-processed surface of the semiconductor device material by means of a CVD method; and a transferring chamber communicating with the surface-processing unit and the CVD unit.